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I purchased a K-Line K29212 set at a swap meet yesterday - this is a Rio Grande Alco PA A-B-A set. All 3 units have smoke and both A units are powered with dual motors. A series of 8-pin connectors links the B unit and trailing A unit to the lead where the R2LC, DCDR, and RS boards reside. So the B unit and trailing A unit are "slaved" to the lead A unit.

This set runs pretty smoothly once it gets going, but the powered units jerk around some (possibly starting and stopping separately at different times) and the set struggles to start moving - I basically have to hit speed 3 on my CAB-2 to get them started and then dial it back so they're not rocketing around the rails. Sounds, smoke, and couplers all work fine and respond to commands from CAB-2, so I suspect this behavior is lack of cruise control and an aging/weak DCDR. However I'm curious if this is a symptom of the wiring setup as well - long connection from lead A unit, through B unit, to trailing A unit for motor control?

Has anyone installed a Cruise Commander M in a set like this? Any issues with a single CC-M driving 4 motors? Any issues with the long wiring connection from lead A unit to trailing A unit? I'd love to hear about some success stories or gotchas others have encountered doing an upgrade like this.

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Bottom line is, if you install a Cruise Commander M in this unit, you'll want to tether the bridge rectifier and heatsink it to allow for the additional load of the extra motors.  Other than that, it should be fairly smooth sailing.

Thanks for the summary @gunrunnerjohn. I read through the linked thread as well. There were some comments in the thread about heat sinking the rectifier directly to the frame - seems like this would require removing that part from the CC-M board and connecting it back via some wires so it can be mounted to the frame regardless of where exactly the CC-M needs to be located. Am I understanding this right and is this what you're referring to when you say "tether the bridge rectifier and heatsink it"?

If anyone has some pictures or more details about how this should be done, please share. I want to make sure I understand what needs to be done before I start down this path. Thanks!

@Norton posted:

K-Line took chances. Plus a DCDR is rated for 8 amps vs 6 amps for a Cruise M. Stall current for four motors is just over ten amps. I guess K-Line thought a DCDR could survive short term locked wheels. Truthfully how many times have you seen two diesels with all 4 trucks locked up?


Interesting - thanks for this additional info. This set does seem to need to "ramp up" to get moving, even after I greased up all the visible gears. But these are currently the only DC motored locos I have without Legacy cruise control or CC-M, so I'm struggling to recall how a vanilla DCDR behaves in a command environment. Perhaps the reason these locos lurch some and don't start moving until ~RR speed 2 is b/c the DCDR has degraded over time due to not being heatsinked properly? I'm hoping upgrading to a CC-M will eliminate this behavior and allow this set to crawl and run at low speeds like it has done for other locos (i.e. my TMCC Amtrak Dash-9).

I'll upload a video of them starting up to demonstrate what I mean

A DCDR has no Cruise capability. It runs the the engine the same as if you were using transformer handles in conventional its just you do it with a red dial vs a handle. Unplug you Legacy base and run the engine in conventional and you will see see it behaves the same. A Cruise M will perform like Legacy with half the speed steps.


I wasn't expecting DCDR to have cruise but want to better understand if this extremely lurchy starting behavior is:

  1. expected from a non-cruise DCDR in command environment
  2. not expected but due to wear of the DCDR itself

I think the answer is #1 but it's been forever since I've run a non-cruise DC locomotive and I don't recall if this is typical behavior or not. I expect a CC-M (properly heatsinked) should eliminate this even when driving all 4 motors?

Here's a video of a start to demonstrate what I mean.


Videos (1)

I installed a tethered CC-M (thanks @gunrunnerjohn). However that didn't resolve the lurches. After some more investigation, it looks like the lurchy starting/low-speed behavior is not due to the DCDR or lack of cruise, but due to motor binding. The rear motor/truck on the lead A-unit is binding at a regular interval and one or both are binding on the trailing A-unit as well. My focus has been on the lead A-unit since I can test it without the B-unit or trailing A-unit. I've taken the rear truck off the lead A-unit about a dozen times now and also tried swapping it with the rear truck from the trailing A-unit. I've done my best to get all the grease and gunk I can access off both the worm gear on the motor and the gear box, then added fresh grease (Labelle 106) to both. I've also tried adjusting the tightness of the screws connecting the motor mount to the truck. Nothing has helped to resolve the binding. Am I looking in the wrong place here? Any thoughts?



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Videos (1)
Last edited by Mike0289

Does the problem follow the motor or the truck? Looking at the truck, you can see bare metal where the worm seems to be making contact with the truck below the worm gear indicating maybe the worm is not on the motor shaft all the way. If thats the case rather than trying to push the gear on further, maybe grind a bit off the end with a dremel.


Thanks for the feedback, gents! The problem does seem to follow the motor, at least to some extent. Swapping rear trucks with the trailing A-unit may have helped some, but binding is still occurring. I'm hesitant to do anything destructive like taking a Dremel to the worm gear, but I think shimming the motor up a little bit should accomplish the same thing so I'll try that.

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